/*
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *  Author: hakanai
 *
 */

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdint.h>
#include <stdbool.h>

#include "libsdb.h"

const uint8_t SDB_FHEAD[5] = { 0x7f, 'S', 'D', 'B', 0 };

static int sdb_fsync(sdb_t *db) {
#if 0 // in case of spiffs usage
  close(db->fd);
  SDB_ASSERT((db->fd = open(db->filename, O_RDWR)) < 0);
#else
  SDB_ASSERT(fsync(db->fd) == -1);
#endif
  return SDB_OK;
}

int sdb_open(char *filename, sdb_t *db) {
  sdb_header_t header;
  uint32_t fsize;
  int fd;

  SDB_ASSERT(!db);

#ifdef ESP_IDF_VERSION
  SDB_ASSERT((fd = open(filename, O_CREAT | O_RDWR)) < 0);
#else
  SDB_ASSERT((fd = open(filename, O_CREAT | O_RDWR | O_SYNC,  S_IRUSR | S_IWUSR)) < 0);
#endif

  SDB_ASSERT((fsize = lseek(fd, 0, SEEK_END)) == -1);

  db->fd = fd;
  db->filename[0] = '\0';
  strcpy(db->filename, filename);

  /*
   * Probably it is a new database
   */
  if (fsize == 0 || sdb_read_header(db, &header) != SDB_OK) {
    /*
     * Maybe the database is corrupted ?
     * The idea of overriting a corrupted files is an extremely stupid.
     */
    if (fsize != 0) // We're done here if so
      SDB_ASSERT(memcmp(header.head, SDB_FHEAD, sizeof(SDB_FHEAD)) == 0);

    SDB_ASSERT(sdb_create_header(&header) != SDB_OK);
    SDB_ASSERT(sdb_write_header(db, &header) != SDB_OK);
    sdb_close(db);

    return sdb_open(filename, db);
  }

  return SDB_OK;
}

int sdb_close(sdb_t *db) {
  SDB_ASSERT(!db);

  if (db->fd >= 0)
    close(db->fd);

  db->fd = -1;
  memset(db->filename, 0, 32);

  return SDB_OK;
}

int sdb_create_header(sdb_header_t *header) {
  memset(header, 0, sizeof(sdb_header_t));
  memcpy(header->head, SDB_FHEAD, sizeof(SDB_FHEAD));
  return SDB_OK;
}

int sdb_write_header(sdb_t *db, sdb_header_t *header) {
  int fd;

  SDB_ASSERT(!db);
  fd = db->fd;
  SDB_ASSERT(lseek(fd, 0, SEEK_SET) == -1);

  header->crc = crc16((const char *)header, SDB_HEADER_SIZE - 2);

  SDB_ASSERT(write(fd, header, SDB_HEADER_SIZE) != SDB_HEADER_SIZE);
  SDB_ASSERT(sdb_fsync(db) == -1);
  return SDB_OK;
}

int sdb_read_header(sdb_t *db, sdb_header_t *header) {
  int fd;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(lseek(fd, 0, SEEK_SET) == -1);
  SDB_ASSERT(read(fd, header, SDB_HEADER_SIZE) != SDB_HEADER_SIZE);
  SDB_ASSERT(header->crc != crc16((const char *)header, SDB_HEADER_SIZE - 2));
  return SDB_OK;
}

int sdb_set_lock(sdb_t *db, int l) {

  SDB_ASSERT(!db);
  sdb_header_t head;

  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);

  head.lock = l;

  SDB_ASSERT(sdb_write_header(db, &head) != SDB_OK);
  return SDB_OK;
}

bool sdb_get_lock(sdb_t *db) {
  sdb_header_t head;
  SDB_ASSERT(!db);
  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  return (head.lock != 0); // true if it has lock
}

int sdb_size(sdb_t *db) {
  SDB_ASSERT(!db);
  sdb_header_t head = { 0 };
  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  return head.r_num;
}

int sdb_read(sdb_t *db, uint32_t num, void *data) {
  uint32_t cursor = SDB_HEADER_SIZE;
  int size, fd;
  uint16_t r_crc;
  sdb_header_t head;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(!data);
  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  SDB_ASSERT(num > head.r_num);
  SDB_ASSERT(head.r_size == 0);

  size = head.r_size;
  cursor += (size * num);
  memset(data, 0, size - 2);

  SDB_ASSERT(lseek(fd, cursor, SEEK_SET) == -1);
  SDB_ASSERT(read(fd, data, (size - 2) ) != (size - 2));
  SDB_ASSERT(read(fd, &r_crc, 2) != 2);
  SDB_ASSERT(r_crc == crc16((const char *)data, size));

  return SDB_OK;
}

int sdb_append(sdb_t *db, void *data, int size) {
  int fd;
  sdb_header_t head;
  uint16_t crc;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(!data);
  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  /*
   * You shall not pass !!!
   * It will never have a queue, otherwise it won't be a (S)imple database.
   */
  SDB_ASSERT(head.lock != 0);

  head.lock = 1;
  if (head.r_size == 0)
    head.r_size = size + 2;

  SDB_ASSERT(sdb_write_header(db, &head) != SDB_OK);
  SDB_ASSERT(lseek(fd, 0, SEEK_END) == -1);

  if (head.r_size == (size + 2)) {
    crc = crc16((const char *)data, size);

    SDB_ASSERT(write(fd, data, size) != size);
    SDB_ASSERT(write(fd, &crc, 2) != 2);

    head.r_num += 1;

    head.lock = 0;
    SDB_ASSERT(sdb_write_header(db, &head) != SDB_OK);

  } else {
  /*
   * The size of records is constant ! Get out of here and RTFM !
   */
    SDB_LOGE("Data size differs r_size: %d vs %d", head.r_size, sizeof(data));
    SDB_ASSERT(sdb_set_lock(db, 0) != SDB_OK);
  }

  return SDB_OK;
}

int sdb_append_fast(sdb_t *db, sdb_header_t *head, void *data, int size) {
  int fd;
  uint16_t crc;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(!data);
  /*
   * You shall not pass !!!
   * It will never have a queue, otherwise it won't be a (S)imple database.
   */

  if (head->r_size == 0)
    head->r_size = size + 2;

  SDB_ASSERT(lseek(fd, 0, SEEK_END) == -1);

  if (head->r_size == (size + 2)) {
    crc = crc16((const char *)data, size);

    SDB_ASSERT(write(fd, data, size) != size);
    SDB_ASSERT(write(fd, &crc, 2) != 2);

    head->r_num += 1;
  }

  return SDB_OK;
}

int sdb_update(sdb_t *db, uint32_t num, void *data) {
  int fd;
  sdb_header_t head;
  uint32_t cursor = SDB_HEADER_SIZE;
  uint16_t crc;
  int size;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(!data);
  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  SDB_ASSERT(num > head.r_num);
  SDB_ASSERT(head.r_size == 0);

  size = head.r_size;
  cursor += (size * num);
  crc = crc16(data, size - 2);

  SDB_ASSERT(lseek(fd, cursor, SEEK_SET) == -1);
  SDB_ASSERT(write(fd, data, (size - 2) ) != (size - 2));
  SDB_ASSERT(write(fd, &crc, 2) != 2);
  SDB_ASSERT(sdb_fsync(db) == -1);

  return SDB_OK;
}

int sdb_delete(sdb_t *db, uint32_t num) {
  int fd, nfd;
  sdb_header_t head;
  uint32_t cursor = SDB_HEADER_SIZE;
  uint32_t follower, fsize;
  int size;
  char data[256];
  int dlen;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  SDB_ASSERT(num >= head.r_num);
  SDB_ASSERT(head.r_size == 0);
  SDB_ASSERT(head.lock != 0);

  head.lock = 1;
  SDB_ASSERT(sdb_write_header(db, &head) != SDB_OK);

  fsize = lseek(fd, 0, SEEK_END);
  SDB_ASSERT(fsize == -1);

  SDB_ASSERT((nfd = open(db->filename, O_RDONLY)) == -1);

  size = head.r_size;
  cursor += (size * num);
  follower = cursor + size;

  SDB_ASSERT(lseek(fd, cursor, SEEK_SET) == -1);
  SDB_ASSERT(lseek(nfd, follower, SEEK_SET) == -1);

  while ((dlen = read(nfd, data, 254)) > 0) {
    /*
     * Something went wrong, the db probably will be dead
     */
    SDB_ASSERT(write(fd, data, dlen) != dlen);
  }

  close(nfd);
  SDB_ASSERT(ftruncate(fd, (fsize - size)) == -1);

  head.r_num--;
  head.lock = 0;
  SDB_ASSERT(sdb_write_header(db, &head) != SDB_OK);

  return SDB_OK;
}

int sdb_clear(sdb_t *db) {
  int fd;
  sdb_header_t head;

  SDB_ASSERT(!db);
  fd = db->fd;

  SDB_ASSERT(sdb_read_header(db, &head) != SDB_OK);
  SDB_ASSERT(ftruncate(fd, SDB_HEADER_SIZE) == -1);
  head.r_num = 0;
  head.lock = 0;
  SDB_ASSERT(sdb_write_header(db, &head) != SDB_OK);

  return SDB_OK;
}

static const uint16_t crc16tab[256]= {
    0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
    0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
    0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,
    0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,
    0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,
    0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,
    0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,
    0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,
    0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,
    0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,
    0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,
    0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,
    0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,
    0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,
    0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,
    0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,
    0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,
    0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,
    0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,
    0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,
    0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,
    0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,
    0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,
    0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,
    0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,
    0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,
    0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,
    0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,
    0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,
    0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,
    0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,
    0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0
};

uint16_t crc16(const char *buf, int len) {
  int counter;
  uint16_t crc = 0;
  for (counter = 0; counter < len; counter++)
    crc = (crc<<8) ^ crc16tab[((crc>>8) ^ *buf++)&0x00FF];
  return crc;
}

